1. Field of the Invention
This invention relates to a gusset bag for photographic photosensitive materials used for packaging a rolled photographic paper, a roll film, and the like.
2. Description of the Prior Art
Gusset bags are widely utilized as packaging bags for packaging various things. It is known that gusset bags can be made of paper, thermoplastic resin film and laminated sheet including a combination of a paper layer disposed on the outside and a thermoplastic resin film layer disposed on the inside so as to be heat-sealable (Japanese Patent KOKOKU Nos. 30177/1981 and 54030/1983. Japanese Utility Model KOKOKU No. 3789/1982, etc.). The sealing of the lower end of the bag using an adhesive tape is also known (Japanese Patent KOKAI No. 575/1981).
On the other hand, photographic photosensitive materials such as rolled photographic paper are necessarily packaged in a packaging bag capable of exhibiting moistureproofness and sufficient physical strength while effectively shielding light since photographic photosensitive materials lose their value upon exposure to light. Therefore, the conventional gusset bag for photographic photosensitive materials is a double-sheet gusset bag composed of two packaging materials, i.e. having an inner sheet and an outer sheet, as shown in FIG. 11. The outer sheet A is composed of an unbleached kraft paper 15 and a light-shielding thermoplastic resin film layer 6a laminated thereto as the heat-sealing layer. The inner layer B is composed of a light-shielding thermoplastic resin film layer 6a, a metal foil layer 5, a bleached kraft paper 18 and another light-shielding thermoplastic resin film layer 6a containing synthetic rubber laminated in that order to each other through adhesive layers 4. In the double-sheet gusset bag, since moistureproofness cannot be attained by heat sealing alone, the bottom sealed portion is turned and further sealed by fixing the turned portion using a hot-melt adhesive.
However, since the above conventional double-sheet gusset bag was made by combining two packaging materials of the outer sheet and the inner sheet in a dark room, workability was difficult and the center seal portion deviated from one bag to another. Moreover, the packaging cost was expensive.